Backplate issue with gloss map

Corona Corona for 3ds Max Issues
1

Pretty sure this is a bug, unless my material is not setup correctly.

It’s very simple to replicate. I have a backplate with a lightmaterial and “Emit Light” switched off. Into this is a conrona tonemap control map and a corona bitmap (normal setup I believe, see attached). I am also using a default sun/sky setup

The problem seems to happen with you add a map including procedural into the gloss map slot or change the gloss value lower than 1. This then creates unwanted shadowing and artefacts. The ground material is just a simple white material. I have noticed before that you get unwanted shadowing using backplates but have only just worked out what it might be.

I am currently using Corona 4 rc3 but I noticed this with previous versions.

Please can you confirm this is correct.

backplate no gloss map on base material.jpg
backplate no gloss map on base material.jpg2020×1538 310 KB

backplate with gloss map on base material.jpg
backplate with gloss map on base material.jpg2020×1538 586 KB

backplate with gloss map only 0.5 gloss value.jpg
backplate with gloss map only 0.5 gloss value.jpg2020×1538 395 KB

2

This is known and very high on our “we would love to fix it, but it’s really hard” list.
See the various light transport issues here: https://coronarenderer.freshdesk.com/support/solutions/articles/5000516180-known-bugs-and-limitations
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3

Thanks for the clarification Maru.

I know you mentioned this was on the very hard list but it would be great to get fixed. There are obviously workarounds but as back-plates are used A LOT in ArchViz a simple workflow would be fantastic!

Thanks